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The Great Train Robbery of 1963 netted $69 million in today’s dollars. The largest bank heists have scored more than $80 million. But “stick-’em-up” bank robberies offer high risks and low rewards: According to the FBI, the average U.S. bank heist yields just $4,200 -- and between 50 and 75 percent of perpetrators get caught.

Robbing a brick-and-mortar bank seems like petty theft compared with a new breed of cybercrime that, according to a growing number of security experts, is siphoning untold millions of dollars from banks and their customers using SSL-evading Trojans and ever more refined phishing techniques.

Every anti-virus and anti-malware vendor can report thousands of bank and e-commerce-specific Trojans designed to steal money and identities, often collectively referred to as Bancos/Banker variants. Yet given the vast investment in quelling consumers’ fears about conducting business online, it’s no surprise that few sources are anxious to provide information that highlights the severity of the problem.

Although the banking officials and security officers contacted for this article refused to be quoted on the record, all of them agreed that online bank fraud is an increasing problem. One banking regulatory security auditor told InfoWorld that in some instances, online bank fraud drains as much as 2 to 5 percent from a bank’s overall revenue.

Mark Sunner, CTO of e-mail security provider MessageLabs, thinks it will take “a single, high-value tipping-point event” to wake up the general public, which would then pressure public officials. “I think the world’s largest bank heist will soon be committed using malware,” he says.

Phishingwith a hook

Phishing remains the weapon of choice for online bank theft -- and the sleight of hand that tricks users into visiting a phishing Web site continues to get more sophisticated. Phishing e-mails now show up with the user’s address, ZIP code, or account information already filled in, indicating that professional criminals are using other, previously compromised resources to gain the trust of consumers.

Yet as phishing gets slicker, users are getting smarter. As the average Joe becomes less likely to type in authentication information in response to an e-mail, more and more cybercriminals are turning to SSL-evading Trojans.

These Trojans install themselves on unsuspecting users’ PCs and either capture user log-on credentials or manipulate transactions after a successful log-on. In both cases, the SSL connection between PC and bank remains intact. The user may think the confidential online transaction is protected against mischief -- but it is not.

That shift has enormous implications. Ever since Netscape released SSL in 1996, consumers have been told that a confirmed SSL-connection icon indicates that it’s safe to conduct online business.

“The problem is,” according to one bank regulatory security auditor, “SSL isn’t broken. SSL states that the connection between your PC’s network card and the bank’s network card isn’t compromised. This is still true. Nobody is sniffing the transaction off the wire. Instead, this is a ‘man-in-the-end-point’ attack.” In other words, the Trojan is sniffing or manipulating the transaction before it is ever sent across the Internet to the bank.

According to Mitchell Ashley, CTO of network security provider StillSecure, “Traditional phishing attacks have duped end-users into clicking on a link, but in the newest evolution, even the most security-savvy can fall victim to attack. Once you’re infected, the game is up.”

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Although the theft of credentials remains the biggest threat to online e-commerce, SSL-evading Trojans are quickly becoming the criminal hacker’s favorite tool, mainly because SSL-evading Trojans can bypass any authentication scheme.

Fighting the last war

Most banks and e-commerce sites fall one step behind, responding to Trojans that steal log-on credentials by creating more complex authentication schemes and implementing two-factor authentication solutions. Today, banks frequently require that users click on-screen, randomized keyboards; type in the random letters of a “magic word”; or enter information from a hardware-based cryptographic key fob. None of these solutions works against the new breed of SSL-evading Trojans.

“It’s not a problem of authentication but one of transactional authorization,” says Bruce Schneier, leading security expert and CTO of Counterpane Internet Security. “No matter how hard you make the initial authentication for the end-user or hacker, the malware can just wait until the authentication is done and then manipulate the transaction.”

For example, you think you’re checking your bank balance or writing an online check to pay a bill, but the Trojan is transferring your bank balance to a bank account in the Cayman Islands.

“The real problem is that we are allowing computers to make transactional decisions for us on our behalf, and the computer really doesn’t know what is right or wrong,” Schneier explains. “The consumer may not be able to see the real transaction to put a stop to the automated authorization approval, and the bank really has no way of knowing that a Trojan is making the decision, and not the customer.”

Even more disturbing is that most banks and regulatory officials don’t understand the new threat, and when presented with it, hesitate to offer anything but the same old advice.

Every bank and regulatory official contacted for this article said they have already recommended banks implement a two-factor or multifactor log-on authentication screen. In general, they expressed frustration at the amount of effort it has taken to get banks to follow that advice. And all complained about the trouble these schemes are causing legitimate customers.

When told how SSL-evading Trojans can bypass any authentication mechanism, most offered up additional ineffective authentication as a solution. When convinced by additional discussion that the problem could be solved only by fixing transactional authorization, most shrugged their shoulders and said they would remain under pressure to continue implementing authentication-only solutions.

They were also hesitant to broach the subject with senior management. It had taken so long to get banks to agree to two-factor authentication, they said, it would be almost impossible to change recommendations midstream. That puts the banking industry on a collision course with escalating attacks.

Verifying real transactions

Workable answers to the SSL-evading Trojan problem aren’t necessarily more inconvenient than two-factor authentication solutions. They just have a different focus: transactional authorization. Solution providers need to realize that any authentication mechanism can be bypassed, and instead focus more on the right long-term answer.

Some banks now send consumers an “out-of-band” authorization code -- that is, not through the PC, but via voice message or text message through another device -- to type in and confirm a particular transaction. Unfortunately, the bank is confirming the transaction as the bank sees it, whereas an SSL-evading Trojan could be manipulating what the customer thinks the bank is getting ready to do. The customer may think he or she is making a small transaction, whereas the bank, because of the Trojan, is closing an account out and a transfer of funds to another bank.

In this case, sending an authorization code to the customer by itself doesn’t work because the consumer is confirming a transaction he or she can’t really see.

A better solution would be to send the consumer the relevant details -- such as the date, from, to, amount, and so on -- along with the authorization code, thus allowing the consumer to confirm the transaction. Some banks and e-commerce sites do this already using in-band e-mail confirmations.

Schneier has his doubts about the out-of-band approach. “These types of authorization schemes would work, but it sounds a little extreme as a solution. Unfortunately, we live in an economic reality where users will not accept extremes. They want convenience.”

Bank officials concur. One regulator said, “Most banks, because of their customers, would probably not accept such an extreme form of authentication. How often would the out-of-band device fail or not be available? Requiring users to confirm every banking transaction out-of-band would not be accepted by today’s consumers.”

The regulator speculated that a better solution might be for the bank to offer out-of-band confirmations as an option and allow the consumer to pick the dollar amount at which the transaction would require additional confirmation measures.

Other bank security officers thought implementing added intelligence on the back end would provide more value. “How about not allowing online transfers to banks and countries with strong ties to crime?” offered one officer. “We could deny any transaction that the bank deemed highly suspicious, like your credit card company does now, and require a second confirmation.”

Close observation of consumer behavior can also help. In one case, nearly 100 customers of one large bank were infected with an SSL-evading Trojan. As usual, the phishing e-mail used mostly legitimate links to the real bank’s Web site. After noticing outside requests to links, most of which were normally referenced from other internal links, the bank’s IT staff realized a Trojan was to blame.

The solution was to rename one of the requested links. If any user went to the real bank’s Web site, the renamed link was now referenced by the legitimate Web site. Only the phishing customers would request the link’s old name, enabling the bank to tell how many of its customers were compromised.

Yunus Emre Alpözen, a consultant for one of the world’s largest banks, says, “Every customer requesting the old Web page link was redirected to a new page that notified them that they were the victims of a phish attack, and how to proceed. We used the phisher’s e-mail against them.”

Self-defense for consumers

Sadly, infection can’t be stopped merely by convincing users not to execute untrusted software. No consumer knowingly installs malicious software, and SSL-evading Trojans can easily go unnoticed by the most careful user.

One of the best defenses is simply to convince consumers to check their online balances frequently. Beyond this, consumers need to lobby financial institutions and move their accounts from institutions that keep their head in the sand.

Banks that require stronger authentication and transactional authorization should be rewarded. Those institutions should also encourage customers to report phishing attacks to the site’s security reporting e-mail address so they can take down fake Web sites or otherwise minimize risk.

Currently, log-on-stealing Trojans are still the No. 1 threat to the banking industry, but SSL-evading Trojans that can bypass any authentication scheme are emerging as a particularly frightening challenge. They need to be dealt with now before consumer confidence in e-commerce goes into serious decline.